The present invention is related to leak rate testing, and is more specifically related to determining the leak rate of a pressurized device during the period where the pressurized gas in the device is undergoing adiabatic cooling.
Systems for performing leak rate testing are known in the art. These systems typically pressurize a device with a gas, and then measure the rate at which the gas escapes from the device. Some systems use the change in pressure over time to determine the leak rate. Other systems use the mass flow into the device to determine the leak rate, such as when the gas is supplied from a source that is at a regulated pressure.
One drawback with existing systems for performing leak rate testing is that they must wait until a period of adiabatic cooling has finished before the leak rate can be measured. Adiabatic cooling occurs because the gas that is used to pressurize the device experiences a temperature rise as it is pressurized. Pressure changes or mass flow changes created by the cooling gas occur at an exponential rate, whereas pressure changes or mass flow changes created by leakage occur at a linear rate. As such, it is difficult to separate the effects of adiabatic cooling from the leakage effects, and leak testing of the device must wait until the adiabatic cooling has progressed to a point where pressure or mass flow changes caused by adiabatic cooling are much less than the pressure or mass flow changes caused by the leak rates that are being measured.
In accordance with the present invention, a system and method for leak rate testing during adiabatic cooling are provided that overcome known problems with leak rate testing.
In particular, a system and method for leak rate testing during adiabatic cooling are provided that model the adiabatic cooling process so that the leak rate can be determined during the adiabatic cooling period by measuring pressure, mass flow rate, or other suitable data.
In accordance with an exemplary embodiment of the present invention, a system for determining a leak rate of a device during an adiabatic cooling phase is provided. The system includes a leak rate training system receiving leak rate calibration data, such as pressure data or mass flow data for a device having a known leakage rate. The leak rate training system generates an adiabatic cooling model from the leak rate calibration data, such as by solving a finite difference equation for one or more unknown process variables that are dependent on the adiabatic cooling parameters of the device. The system further includes a leak rate detection system receiving the adiabatic cooling model and leak rate data and determining a leak rate component of the leak rate data using the adiabatic cooling model, such as by using the variable values determined through solving the finite difference model to interpolate between the leak rate calibration data that was gathered using known leakage rates.
The present invention provides many important technical advantages. One important technical advantage of the present invention is a system and method for measuring leak rates during adiabatic cooling that use a model of the change in a leak rate metric, such as pressure or mass flow, to determine the change in the leak rate metric caused by adiabatic cooling. The invention allows leak rate data to be extracted from the leak rate metric during the adiabatic cooling period, such that the leak rate can be determined faster than in prior art systems and methods.
Those skilled in the art will further appreciate the advantages and superior features of the invention together with other important aspects thereof on reading the detailed description that follows in conjunction with the drawings.